1. Field of the Invention
The present invention relates generally to methods and compositions for treating fungal nail infections. More particularly, the present invention relates to the treatment of fungal nail infections by oxygen deprivation.
Many adults suffer from chronic fungal infections of the fingernails or toenails. Most such infections are causes by obligate aerobic fungal species, usually "dermatophytic" or yeast-like fungi, which infect the nail plate itself. Although not usually imposing a significant health risk, such nail infections frequently cause the nail to become deformed, discolored and/or blackened. Thus, there is a strong desire among infected individuals to treat the infection and return their nails to a normal appearance.
Unfortunately, such fungal nail infections have proven to be very resistant to treatment. Systemic administration of anti-fungal drugs is hindered by limited blood circulation in the nail bed and poor transport to the nail plate, requiring high dosage levels for long periods of time. Such high drug dosages can have adverse side effects, and it has been found that clearance of the infection is often only temporary. Thus, systemic treatment must often be continued indefinitely.
Topical administration of anti-fungal drugs also suffers certain limitations. The nail plate is a relatively thick structure which inhibits penetration of the drug being applied. Moreover, the topical application of creams, lotions, gels, and the like, is often lost or dissipated in relatively short times. Although attempts have been made to incorporate such topically active anti-fungal drugs into film-forming compositions, e.g., nail polishes or lacquers, to improve drug persistence, such approaches have not proved entirely satisfactory. While removal of the nail can improve topical drug treatment, the ability to maintain a constant supply of the drug to the nail bed remains problematic.
For these reasons, it would be desirable to provide improved methods and compositions for treating fungal nail infections. Such methods and compositions should be effective in treating the initial infection as well as inhibiting spread of the infection to other nails and recurrence of the infection after treatment has been completed. It would be desirable to provide treatment methods and compositions which do not rely on the administration of anti-fungal drugs, either systemically or topically. In particular, the treatment methods and compositions should avoid the side effects which can accompany drug administration. Additionally, it would be desirable to provide methods and compositions which can provide cosmetic cover-up during the treatment period.
2. Description of the Background Art
Treatment of nail fungal infections with anti-fungal drugs incorporated in a film-forming vehicle is described in PCT application WO 87/02580 and UK Patent Application 2 202 743A. Other compositions incorporating anti-fungal drugs for topical treatment of nail fungal infections are described in U.S. Pat. Nos. 4,810,498 and 3,395,236. Fungi-Nail.RTM. is a commercial formulation for the topical treatment of fungal nail infections which includes 2% salicylic acid in combination with anti-fungal drugs. The formulation does not form an oxygen barrier when applied to the nail.